In the news: Kashiwa hotspot news shows topography and other factors can concentrate radiation in hotspot; U of Tsukuba researchers find new type of algae better than zeolite at absorbing radioactive materials; thorium reactors not the solution?

One of this morning’s TV (channel 4) news reports had more details of how the contamination in the Kashiwa hotspot occurred, with film clips showing the topography of the site, and diagrams showing that the rainwater falling on and seeping into the hillside, being carried by a ditch channel that led to the pooling of cesium in the “hotspot” where the break in the ditch was.

Rainwater contaminated with radioactive fallout from the Fukushima No. 1 Nuclear Power Plant likely leaked through a broken ditch, causing high levels of radioactive cesium in the soil in Kashiwa, Chiba Prefecture, the central government said Oct. 23.

The government made the announcement after the Education, Culture, Sports, Science and Technology Ministry conducted an on-the-spot inspection of a hot spot emitting up to 276,000 becquerels of radioactive cesium per kilogram of soil on a plot of public land in the city’s Nedo district.

The ministry’s findings revealed widespread fallout of radioactive materials from the crippled Fukushima nuclear plant. The city will consult with the ministry about how to decontaminate the affected area.

According to the ministry’s Office of Radiation Regulation, the wall of a 30-centimeter deep and 30-centimeter wide concrete ditch adjacent to the highly radioactive hot spot had been broken over a 0.5- to 1-meter stretch in width. The rainwater ditch downstream has been built along a city road.

Water levels in the ditch are not clear but it is assumed that accumulative rainwater upstream had leaked from the broken ditch.

The ministry’s inspection on Oct. 23 found maximum airborne radiation of 14.6 microsieverts per hour near the ground and about 2 microsieverts one meter above ground when the tarps covering the hot spot were lifted. Maximum radiation around the tarp came to 0.6 microsieverts.

Takao Nakaya, head of the Office of Radiation Regulation, said radiation levels in spots of assembled rainwater tend to be high as in the case of places below gutters. He also said hot spots in similar circumstances may be found in the metropolitan region.

Nakaya said there was little possibility that soil or ash contaminated with radioactive materials had been dumped.

The hot spot in Kashima has been used as a public square since city-run houses were demolished in 1995.

The hot spot was discovered by a resident who was strolling in the area carrying a dosimeter and the city was notified on Oct. 18. Local government officials checked on Oct. 21 and found radiation of 57.5 microsieverts per hour. The central government’s decontamination guidelines stipulate that a radiation level of 0.23 microsieverts per hour is likely to top an annual exposure of 1 microsieverts and thus is subject to decontamination work.

The ministry had initially planned to conduct the inspection on Oct. 24 but moved it up one day due to a request from the Kashiwa city government.

Meanwhile, Yoshihisa Matsumoto, associate professor of radiation biology at the Tokyo Institute of Technology, speculates that such heavily contaminated soil was found in Kashiwa because the entire city is full of hot spots. But he says it poses no harm to humans even if internal radiation is taken into account.

Atsushi Kasai, former laboratory chief of the Japan Atomic Energy Research Institute (Japan Atomic Energy Agency) who researched the 1986 Chernobyl disaster, says radiation levels in Kashiwa are one to two digits below Chernobyl levels and the city’s contaminated area is very limited.

But he warns, “There is a possibility that similar phenomena will be seen in various locations. The ministry should simultaneously announce not only the density of radioactive materials but radiation doses serve as a barometer for health risks.”

CHIBA — “The science ministry said Sunday that the high radiation detected on city-owned land in Kashiwa, Chiba Prefecture, is emanating from cesium that was probably ejected by the crippled Fukushima nuclear plant, contradicting the city’s earlier claims.

When the Kashiwa Municipal Government first got wind of an airborne radiation reading of 57.7 microsieverts per hour at the site, it said the radiation was unlikely to be related to the Fukushima disaster as it was in such a tiny area.

On Sunday, the ministry and city workers found a side ditch near the spot during a joint survey and said it is highly likely that rainwater tainted by fallout from the Fukushima plant flowed into nearby soil.

“The possibility is high that cesium carried in rain water condensed and accumulated in the soil,” said Takao Nakaya, heads of the science and education ministry’s radiation regulation office.

Part of the ditch, which is about 30 cm deep, was broken and the water seems to have leaked from there, ministry officials said.

“We’d like to take (the finding)s back to the office and start decontamination work as soon as possible,” Nakaya said.

Local residents said that they were deeply concerned.

“This was a place where children always played around. I’m worried about whether the radiation had any effects on the children,” said Shigeru Ono, 74.

Earlier surveyors who dug deeper into the hot spot soil recorded stronger radiation, leading some experts to speculate the tainted soil came from elsewhere and was deliberately buried.

But the ministry confirmed the same day that rainwater is leaching from the ditch and into the soil at the hot spot.

Up to 276,000 becquerels of cesium per kilogram of soil was detected 30 cm below the surface there Friday after abnormally high airborne radiation was detected earlier in the week, the city said.

“If fallout from the Fukushima plant naturally falls onto the ground, it’d be unthinkable that the radiation level would be higher deep in the soil than on the surface,” said Masako Sawai, researcher at Citizens’ Nuclear Information Center, a Tokyo-based antinuclear activist group, before the ministry press conference Sunday. …”

Japan’s science ministry has launched a telephone hotline to deal with public concerns about radiation exposure in areas outside Fukushima Prefecture. The prefecture hosts the damaged nuclear complex.

The ministry set up the hotline after radiation monitoring by local governments and citizens’ groups found a number of locations within the Tokyo Metropolitan Area with levels exceeding government limits.

The ministry is asking local governments and citizens’ groups to tell it if they find sites where the hourly radiation dose at one meter above the ground is more than one microsievert higher than nearby areas.

One microsievert per hour is the government-set limit for determining whether topsoil at school playgrounds should be removed, using state subsidies.
The ministry is also asking the local governments to carry out simple decontamination work, such as clearing mud from ditches if necessary.

The ministry says the central government will support decontamination efforts if radiation levels remain more than one microsievert higher than nearby areas even after the cleaning.

The ministry has posted a guideline on its website on how to properly measure radiation levels, such as the right way to hold the dosimeter and the time needed for a reading.

The Forestry Agency has decided to allow local governments to use plots of land in state-owned forests to temporarily store soil and rice straw contaminated with radioactive substances from the crippled Fukushima No. 1 nuclear power plant.

Local governments will be responsible for preparing the land for the temporary storage sites, while the central government will shoulder the cost using its reserve fund for reconstruction.

Many local governments affected by the March 11 disaster are having difficulty securing storage sites for contaminated soil and other matter.

Providing land in the state-owned forests may help resolve this problem.

The sites will store soil removed in the process of decontamination and rice straw contaminated with radioactive materials.

Local governments may ask to be allowed to store sludge from the water supply and sewage systems, as well as ash produced by incinerating it.

In principle, the temporary storage sites will be built in forests within the jurisdictions of local governments that have collected contaminated soil.

If there are no state-owned forests with the jurisdiction of a local government, it will decide what to do in consultation with other local governments.

The sites will be located tens or even hundreds of meters from residential areas.

If a forest is near a water source, local governments will be required to consult with governments downstream before building temporary storage sites.

Contaminated soil and other matter will be encased in waterproof materials. If the quantity to be stored is large, the contaminated material will be placed inside concrete containers or surrounded by concrete walls.

As the sites are defined as temporary storage facilities, contaminated matter will not be buried.

According to an Environment Ministry estimate, up to 28 million cubic meters of contaminated soil in Fukushima Prefecture should be removed as it is assumed to have a radiation dosage of 5 millisieverts or higher per year.

If the soil is evenly piled up one meter high, the total area would be about 65 square kilometers, equivalent to half the area inside Tokyo’s Yamanote loop railway line.

The central government has asked municipal governments to secure temporary storage sites until proper storage facilities have been completed.

After local residents strongly opposed plans to store contaminated soil in school yards or playgrounds, Iitatemura and Nihonmatsu, both in Fukushima Prefecture, asked the Forestry Agency to come up with other methods.

The Agriculture, Forestry and Fisheries Ministry has found that about 7,200 tons of rice straw have been stored in farmers’ warehouses and other places in eight prefectures, including Hokkaido, Miyagi and Fukushima, as it could not be disposed of.

The sludge from the water supply and sewage systems and the ash, which cannot be disposed of due to radiation contamination, totaled about 130,000 tons as of September in Tokyo and 14 other prefectures.

The Forestry Agency will start checking for radioactive substances in cedar pollen in Fukushima Prefecture as early as next month in response to the crisis at Tokyo Electric Power Co.’s Fukushima No. 1 nuclear power plant, the agency said.

There is very little data in Japan or elsewhere in the world about pollen from plants grown in areas with high levels of radiation. If high levels of pollen-borne radiation are found, the Environment Ministry plans to release the data at the end of this year together with its forecast of the expected amount of cedar pollen to be dispersed in the air next spring.

The agency plans to pick male cedar flowers in the no-entry zone and check them for radioactive cesium, it said.

“As it will be the first such survey, we honestly don’t know how much we will find. We’d like to obtain objective figures by making an accurate survey,” an official of the agency said.

According to the agency and the Fukushima prefectural government, the prefecture has about 184,500 hectares of national and private cedar forests, accounting for about 20 percent of the total forests in the prefecture.

The agency has yet to decide the size of the areas to be surveyed, it said.

According to the Social Welfare and Public Health Bureau of the Tokyo metropolitan government, the wind sometimes carries cedar pollen more than 200 kilometers.

“It depends on the velocity and direction of the wind. Pollen is said to fly from dozens to hundreds of kilometers. When a survey was conducted by helicopter, pollen was found as high as 5,000 meters in the air. It is highly likely that pollen from Fukushima Prefecture reaches the Tokyo metropolitan area,” said Norio Sahashi, a visiting science professor at Toho University and an authority on pollen.

But specialists say people do not have to worry too much about the effect of the pollen on human bodies.

“Even if pollen from radiation-contaminated areas does contain radioactive cesium, the amount people will take in is expected to be very limited. From the standpoint of radiation exposure, the amount is at a level that can be ignored,” said Satoshi Yoshida, an expert on radiation ecology and a senior researcher at the Research Center for Radiation Protection of the National Institute of Radiological Sciences.

Yoichiro Omomo, special advisor at the Institute for Environmental Sciences, said, “Those who are allergic to cedar pollen do not need to worry too much as long as they take ordinary measures.”

In late March, many inquiries were received by the Meteorological Agency and local governments about a yellowish residue found in gardens and elsewhere in the Kanto region.

Many residents apparently feared the residue was a radioactive substance from the crippled nuclear power plant, but it turned out to be pollen from the Kanto region.

Mini hotspot emerges in Kashiwa, according to the city’s public announcements, it is a cesium deposit (read on details posted below)

CHUO, Yamanashi — A new type of algae is better at absorbing radioactive strontium and iodine than a mineral currently being used to treat radioactively contaminated water, say scientists.

According to a research group, the new algae, called “Parachlorella sp. binos” or “binos” for short, is better at absorbing some radioactive materials than is zeolite, which is being used at the Fukushima No. 1 Nuclear Power Plant to treat radioactively contaminated water.

Binos has already been commercialized by Japan Biomass Corp., a University of Tsukuba-affiliated startup, for the cleaning of sewage, and the corporation conducted joint research with the Kitasato Institute and other groups to explore applying binos to cleaning radioactively-contaminated water as well.

Researcher Hiroki Shimura of the University of Yamanashi’s medical department agreed to help with the research and conducted tests with the algae on radioactively contaminated water collected from ditches in Namie, Fukushima Prefecture, from April through July.

He put 100 grams of binos each into one-liter samples of contaminated water, one with two megabecquerels of radioactive cesium-137, one with two megabecquerels of radioactive strontium, and one with three megabecquerels of radioactive iodine. After 10 minutes, the strontium was around 80 percent removed and the cesium-137 was around 40 percent removed. After 24 hours, the iodine was about 40 percent removed.

Binos that has been processed into jelly-like spheres is seen at left, and binos spheres that have been dried are seen at right at the University of Yamanashi, Chuo, Yamanashi Prefecture. (Mainichi)

By contrast, zeolite did not absorb iodine at all. After about one hour, zeolite absorbed only around 60 percent of the strontium in its mixture, compared with 95 percent absorbed by the binos algae.

Because binos is an alga, it can be easily grown where there is light and carbon dioxide. Researchers say that if dried, the weight of binos shrinks to 1/20, which could help simplify dealing with it after it has been used to absorb radioactive materials.

The researchers are talking with power plant equipment makers over introducing the algae to work at the Fukushima plant, and a demonstration of using the algae to treat radioactively contaminated soil and then storing the algae is planned in the city of Date, Fukushima Prefecture, at the end of October. The demonstration will be conducted by multiple corporations including Japan Biomass Corp.

TOKYO (Kyodo) — Two boys in Fukushima Prefecture were found to have been internally exposed to the highest levels of radiation detected during checks conducted on nearly 4,500 local residents in the wake of the nuclear crisis at the Fukushima Daiichi power plant in the northeastern prefecture, the prefectural government said Thursday.

The level of exposure is estimated to be equivalent to 3 millisieverts during their lifetime, which would not have harmful effects on their health, according to government officials. The local government has not disclosed the boys’ exact ages, saying only that they are between 4 and 7 years old.

The boys, who are from the town of Futaba, which partly hosts the plant that was severely damaged by explosions after the March 11 earthquake and tsunami, showed the highest levels of internal exposure among 4,463 residents of 13 high-risk municipalities tested between June 27 and Sept. 30, the officials said.

Among others tested, eight people measured 2 millisieverts, six 1 millisievert and the remaining 4,447 below 1 millisievert, they said.

They were tested using whole body counters either at the National Institute of Radiological Sciences in Chiba city or the Japan Atomic Energy Agency in Tokaimura, Ibaraki Prefecture. Estimates for adults were calculated to measure accumulated radiation exposure in the coming 50 years, and for children until they reach the age of 70.

OTSU, Japan (Kyodo) — A group of residents from Shiga and nearby prefectures plan to file a lawsuit to suspend the restart of two nuclear reactors at the Tsuruga plant in neighboring Fukui Prefecture, arguing an accident at the plant would contaminate Lake Biwa, their water source, and be life-threatening, according to sources involved in the suit.